Presentation on theme: "The beginning... When do you think the first usage of radio waves was?"— Presentation transcript:
0The History of Radio and Radio Astronomy! Radio waves haven't changed, but our usage of them has...
1The beginning... When do you think the first usage of radio waves was? What was the first piece of technology to use them?
2The beginning... - It all starts with math - James Clerk Maxwell, in 1864, showed using mathematics that electromagnetic force could be propagated through free space at any wavelengthHe also went on to calculate the speed of light to within 4% of what we know today!- Wasn't until 1888 that Heinrich Rudolf Hertzdemonstrated in the lab that electromagneticwaves existed by producing and detectingradio waves
3First uses: - Wireless telegraph It is not very clear as to whom to credit with the overall invention of this device.First device to be used to successfully transmit a transatlantic message was invented by Guglielmo Marconi.Just like the regular telegraph machines, the wireless version also sent information using Morse Code.
4Radio's Evolution: - Soon after messages were successfully sent via Morse code, it was hypothesized thatspeech information could be encoded and sent via radio waves.This was achieved by Reginald Fessenden by Amplitude Modulation (AM radio) in 1906
5Radio's Evolution: - After World War I, AM Radio took off thanks to the company RCA- AM lingered around for awhile until the 1930s when amatuer radio operators started experimenting with frequency modulationFM Radio gets its official start in 1933 thanks to Edwin Armstrong1938 marks the famous Orson Welles broadcast of "The War of the Worlds"
6Things take off...- TV gets invented around the 50s and "Radio" starts to take a backseatTV broadcasts also rely on radio waves!- At this point a lot of things start to happen including the transistor radio, radio satellites, and its conversion into the digital age (all your technologies rely on the transmission and reception of radio waves!)- The important thing is how radio waves started to be used in astronomy in the 1930s...
7Interlude: A good breakdown of the history of Radio:
8Radio Astronomy:- The history of Radio astronomy again starts with Maxwell and Hertz- From these predecessors, many scientists believed they could detect radio emissions from celestial objects2 notable scientists who experimented with this early on were Thomas Alva Edison and Sir Oliver J. Lodge in the 1890's.
9Karl Jansky: - In the early 1930s Karl Jansky was assigned by the Bell Telephone Company toinvestigate sources of static that might interfere with radio transmissions.- Jansky build an antenna that detected radiowaves of 20.5 MHz.
10Karl Jansky cont.- Using his antenna, Jansky discovered three static sources:Nearby thunderstormsDistant thunderstormsan unknown hiss that occurred approximately once a day....- What was that unknown hiss?https://admissionblog.usc.edu/files/2013/05/Question-Mark.jpg
11Karl Jansky cont.- It turns out, the faint hiss that Jansky discovered wasn't following the 24-hr day of the sun, therefore wasn't coming from the sun.Instead it followed a sidereal day (23 hrs. 56 mins) which followed the path of a distant starTurned out he discovered the radio emissions of the center of our galaxyHis results of this were widely publicized in 1933, but sadly he never worked in radio astronomy again
12Grote Reber:- Was very interested in Jansky's discovery in 1933, but was unable to get a job at an observatory due to it being the great depression- He decided that wasn't going to stop him:Built his own (very impressive) radio telescope in his backyard
13Grote Reber cont. - His telescope used a parabolic dish design Focuses all wavelengths to a single focus- After many attempts, he confirmed Jansky'sdiscovery in 1938- Overall, he used his telescope to chart the night sky and keep track of the "brightness" of radio waves in our galaxyUsed these to make the first "pictures" using radio waves in the form of contour maps (based on the brightness of the radiationdetected)
14Important times in Radio Astronomy: - 1942: James Stanley Heysuccessfully detects radioemissions from the sun- 1944: Jan Oort and his studentHendrik C. van de Hulstpredict the existence of the21-cm hydrogen line (hugein astrochemistry)- 1951: Edward Mills Purcell andHarold Irving Ewen discoverthe 21-cm hydrogen line
15Other important times: - In the 1940s radio interferometry was used to perform the first high resolution radio astronomy observations- 1967: First VLBI (Very Long baselineInterferometry) done by Canadian and U.S.researchersFrom this point it was realized VLBI could be used to perform many useful tasks in radio astronomy- From this point on, VLBI has been on the dominanttechniques in the field of radio astronomy as it allowedfor greater and greater resolution as the baselinesbecame greater and greater
16More Dates:- 1963: the largest radio telescope to date is built in Arecibo, Puerto Rico (1000-ft. aperture)
17More Dates: - 1966 and 1967: Shapiro's 4th test The '4th' test of Einstein's general relativity done at Haystack Observatory
19Local Efforts:- A lot of improvements in radio astronomy wouldn't have happened if it wasn't for the efforts of MIT's Radiation lab during and after WWIIBefore, during and after the war, the military invested a lot of research money into the development of better radar systems.
20Local Efforts continued: - These two sources do a good job showing the role MIT's Rad lab played in the war efforts:
21Post-War efforts:- During the Cold War, great emphasis was placed on long range detection of ICBMsAt the time, radar only worked a maximum distance of the horizonMade it necessary for much longer range of detectionMilitary again gave much of the refining work to MIT, this time at Lincoln Labs:
22How research is done:- The previous links are perfect examples of how research is done in the scientific community:The government / military see shortcomings in technologyResearch money is given out to figure out how to improve the technology (the more pressing, the more money)rinse and repeat...
23Example: - Military needs a longer range radar for ICBM detection: Lincoln Labs given R&D money and develops SAGE- Military notices a lot of false alarms due to ionosphere and auroras:MIT finds out what is causing these and figures out how to fine-tune the system- The improvements not only beneficial for the military, but for the scientific community as a whole
24There is so much more... But not enough time to cover it all! If you are interested, look up research done in:- Incoherent Scatter Radar (Space Weather)- Sgr A* or NGC4258 (Black Holes!!!!) /- Event Horizon Telescope- Geodesy (plate tectonics)- VLBI- Astrochemistry (spectroscopy, chemicals in space, etc.)- MASERs (basically radio lasers, everyone loves lasers!)